1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) module, more particularly, to a chip on film (COF) type LCD module.
2. Description of the Related Art
There are many types of flat panel display devices, including plasma display panels (PDPs), field emission displays (FEDs), and the widely used LCDs. FIG. 1 is an exploded perspective view of a mounting structure of an LCD module 100 according to related art. The LCD module 100 has a liquid crystal panel 110 and a polarizing sheet 108 disposed on the liquid crystal panel 110. The liquid crystal panel 110 consists of a lower substrate 110a, an upper substrate 110, and a liquid crystal layer (not shown) in between. The LCD module 100 further includes a backlight assembly. The backlight assembly comprises multiple prism sheets 116, 117, a diffusion sheet 118, a light guide plate 120, and a reflective plate 122. Additionally, the LCD module 100 includes a main support 130 where the liquid crystal panel 110 and the backlight assembly are installed. The liquid crystal module 100 also includes a top case 140 that fastens the liquid crystal panel 110 to the main support 130 and protects the liquid crystal panel 110 from external impact.
Although not shown in FIG. 1, a lamp housing including at least one lamp is generally installed in the main support 130. The at least one lamp is connected to an inverter (not shown) and emits light toward the liquid crystal panel 110. The light guide plate 120 is disposed under the diffusion sheet 118. The reflective plate 122 is disposed between the light guide plate 120 and the main support 130. The light guide plate 120 receives light emitted by the lamp and directs the received light to its output surface so that the light emitted by the lamp can reach the liquid crystal panel 110 via the diffusion sheet 118 and the prism sheets 117, 116. The reflective plate 122 reflects light emitted by the lamp toward the liquid crystal panel 110 to prevent loss of light and improve efficiency. The light emitted by the lamp and propagated through the backlight assembly generates images on the display panel while the liquid crystal panel 110 is operated and driven.
Although not shown in FIG. 1, the LCD module 100 includes a bottom cover adjacent to the main support 130 to protect the elements for the LCD module 100. The main support 130 supports the backlight assembly and the liquid crystal panel 110. The top case 140 fastens the liquid crystal panel 110 and the backlight assembly into the main support 130 by coupling them with the main support 130. The main support 130 and the top case 140 protect the liquid crystal panel 110 from external impact. The main support 130 is generally made of a plastic material having a sufficient impact resistant.
In the related art LCD device shown in FIG. 1, the top case 140 has a rectangular shape and an internal rectangular opening. The rectangular opening exposes a display area of the underlying liquid crystal panel 110 such that images are displayed on the exposed display. The liquid crystal panel 110 is driven by input signals transmitted from gate and data driving integrated circuits (ICs). Furthermore, a gate printing circuit board (PCB) and a data PCB control the gate and data driving ICs, respectively.
FIG. 2 is a schematic top plan view of a related art LCD module, and conceptually illustrates driving ICs, PCBs and their connection to a liquid crystal panel. As shown in FIG. 2, a gate driving IC 167 and a data driving ICs 177 are formed on a first flexible film 165 and a second flexible film 175, respectively, and connected to the liquid crystal panel 110 via the first and second flexible films 165 and 175. Additionally, the gate and data driving ICs 167 and 177 are communicating with gate and data PCBs 160 and 170, respectively, via the first and second flexible films 165 and 175. Although not shown in FIG. 2, the first and second flexible films 165 and 175 include printed circuits that transmit signals from the gate and data PCBs 160 and 170 to the gate and data driving ICs 167 and 177. Also, the first and second flexible films 165 and 175 transmit signals from the gate and data driving ICs 167 and 177 to the liquid crystal panel 110.
The LCD module of FIG. 2 includes a grounding path G1 to protect the above mentioned circuitries from static electricity to thereby prevent electrostatic damage. As shown in FIG. 2, the grounding path G1 interconnects the data PCB 170, data driving IC 177, gate driving IC 167 and gate PCB 160, and ground. This grounding method will be explained in more detail with reference to FIG. 3.
FIG. 3 is a bottom plan view of the LCD module 100 of FIG. 2, and schematically illustrates the grounding method. As shown in FIG. 3, the gate PCB 160 is electrically connected to the top case 140 via a first conductive tape 169 so that the gate PCB 160 has a stable ground connection. The first conductive tape 169 may be formed of copper (Cu), for example. In the related art LCD module 100, the gate PCB 160 is sufficiently grounded to the top case 140 because it has an area large enough to be connected via the first conductive tape 169. Meanwhile, the data PCB 170 is electrically connected to the top case 140 via a second conductive tape 179 so that the data PCB 170 has a stable ground connection. The second conductive tape 179 may be formed of aluminum (Al), for example. In the related art LCD module 100, since the top case 140 is coupled with a grounded bottom cover 180, the LCD module 100 has a stable ground connection, any accidental static electric discharge will not cause damage to the circuitries. However, this LCD module 100 is not desirable due to the number of fabrication process steps and high fabrication costs.
FIG. 4 is a schematic top plan view of another related art chip on film (COF) type LCD module. As shown in FIG. 4, this LCD module includes the liquid crystal panel 110, the gate and data driving ICs 167 and 177, and the data PCB 170. However, unlike the LCD module 100 of FIG. 2, the LCD module of FIG. 4 does have a gate PCB. The gate PCB is not installed so as to reduce the process steps of fabricating the LCD module. Furthermore, the gate PCB makes a thinner module with increased spatial efficiency. When the gate PCB is not installed, the gate driving ICs 167 are controlled by the data PCB 170 and supply signals to the liquid crystal panel 110 via the first flexible films 165. Namely, the data PCB 170 controls both the gate and data driving ICs 167 and 177. Additionally, a grounding path G2 is installed to electrically connect the data PCB 170, the data and gate driving ICs 177 and 167. Unlike the LCD module of FIGS. 2 and 3, since no gate PCB is provided, the gate driving ICs 167 may not be grounded sufficiently to the top case. Namely, the LCD module of FIG. 4 does not have a stable grounding such that it can efficiently discharge static electricity so as to avoid damage to the circuitries. Therefore, the LCD module can be damaged by static electricity or have noise in the displayed images.